20181110, 17:50  #12 
Einyen
Dec 2003
Denmark
6433_{8} Posts 
B2=B1*100 is actually low. GMPECM chooses a much higher B2 if you do not specify it yourself:
B1=11000, B2=1684420 B1=50000, B2=15446350 B1=250000, B2=183032866 B1=1000000, B2=974637522 B1=3000000, B2=4592487916 B1=11000000, B2=30114149530 So roughly B2=3.8 * B1^{1.4} I think ideally stage2 should take the same amount of time as stage1. Last fiddled with by ATH on 20181110 at 17:51 
20181110, 17:58  #13  
Sep 2003
A1B_{16} Posts 
Quote:
Quote:


20181110, 18:03  #14  
Sep 2003
13×199 Posts 
Quote:
For mprime I'd say the factor of 100 rule of thumb would still apply. No sense spending a ton of time pursuing diminishing returns on one ECM curve when you can just start another curve and maybe a factor will pop out much more easily with that one. 

20181110, 22:33  #15 
"GIMFS"
Sep 2002
Oeiras, Portugal
2×19×41 Posts 

20181111, 00:07  #16  
Random Account
Aug 2009
Not U. + S.A.
100011101100_{2} Posts 
Quote:
Now, we get back to RAM and ontopic. The most I can allocate on this I7 is 2.5GB. When I built this last year, I had intended to add more RAM later on. That didn't happen. So, it still has 8GB. As a point of reference, my much older HP has 4GB and seems to do quite well. As B2 increases, so does the amount of RAM required, or so it seems. George talks about memorythrashing in his documentation. I would prefer to avoid that. In my experimentation this morning, I tried squeezing the amount for Stage 2 RAM lower and lower. The only result I saw was that Stage 2 would take longer to run. 

20181111, 01:01  #17  
Sep 2003
13·199 Posts 
Quote:
One reason that GMPECM can use much larger B2 is because it uses a much more efficient algorithm for stage 2. But it can only be used for small exponents. As lycorn mentioned, for anything bigger than about 40k, you need to use mprime instead. Quote:
With B1 = 250k and B2 = 100 × B1 and exponents in the 100k range, I don't think it will need anywhere near 2.5 GB actually. If you run with mprime d, then when it starts ECM stage 2 it will output lines of the form Using ____MB of memory in stage 2. Obviously this will be no greater than the amount of kB you specified in the Memory= line in your local.txt file. Last fiddled with by GP2 on 20181111 at 01:03 

20181111, 02:01  #18 
Einyen
Dec 2003
Denmark
6433_{8} Posts 
I did not mean of for you to not enter B2 value in Prime95, it is not possible. I was just illustrating that the "standard" B2 in GMPECM is so high, and yes this algorithm will not work for higher numbers. But my point was that B2=100*B1 is not crazy high and it might be a bit lower than we could do.
I do think that the optimal values are such that stage1 time = stage2 time, so if you feel like optimizing and your stage2 time is way faster than stage1 you could raise B2 provided you give Prime95 enough RAM, otherwise it will just be slow if you do a big B2 with low RAM, it has to split stage2 in too many stages. But otherwise just leave it at B2=100*B1, or lower it to 10*B1 if you want, it is your clock cycles and power bill to spend like you want 
20181112, 13:19  #19  
Random Account
Aug 2009
Not U. + S.A.
2^{2}·571 Posts 
Quote:
Windows 10 has a pretty good Task Manager. As I was testing, I would watch the RAM usage by Prime95. I found that I could go up to 4,096 MB with no problems. 5,120 may even be possible, but I don't see the need. Windows 10 compresses its memory contents onthefly. For some strange reason, I set this using powers of 2. Imagine that. Running all this does not seem to have a lot of affect on my power bill. My rate is 0.1286 USD per kWh. It stays in that area year round. About mprime, I've never ran any flavor of Linux. I've watched local friends run it. It sails over my head. Too many years of MS. Edit: Look at the examples below. Are the bounds too close to each other from one test to the next for the same exponent? Code:
ECM2=<ID>,1,2,<Exponent>,1,10000 1000000,<Curves>,"<Known factors>" ECM2=<ID>,1,2,<Exponent>,1,11000 1100000,<Curves>,"<Known factors>" Last fiddled with by storm5510 on 20181112 at 13:43 Reason: Question 

20181112, 17:35  #20 
"Curtis"
Feb 2005
Riverside, CA
17×317 Posts 
ECM uses a random seed for its work, and each seed does work independently of other seeds. You can use the same bounds as many times as you like without repeating work. It's normal to complete a "level" of ECM testing without changing bounds (though some folks jump to higher bounds before a previous level completes; mersenne.org converts these curves to count work reasonably accurately).
So, unlike PM1 work, don't worry about using the same bounds multiple times. 
20181113, 03:01  #21  
Random Account
Aug 2009
Not U. + S.A.
2^{2}·571 Posts 
Quote:
After doing some observation while Prime95 was running, I saw that the "at prime" value does not exceed B1 in stage 1 or B2 in stage 2. This would explain the variation I see in the bounds when looking at the recent data on mersenne.org. This would sort of support the argument that some say wider bounds are better. The formula that ATH posted above goes well beyond B2 = B1 * 100. With a B1 of 10,000, the typical B2 would be 1,000,000. With his formula B2 becomes 1,512,807. Of course, this is not set in stone. He also indicates the time for Stage 1 and Stage 2 should be about the same. In order to match this, I would have to further increase B2 by 27%, more or less. 

20181113, 04:41  #22  
Jun 2003
2^{2}×3×449 Posts 
Quote:


Thread Tools  
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
How to use prime95 for stage 1 & GMPECM for stage 2  Prime95  Lone Mersenne Hunters  118  20220704 18:19 
Stage 1  G_A_FURTADO  Information & Answers  1  20081026 15:21 
Stage 1 with mprime/prime95, stage 2 with GMPECM  D. B. Staple  Factoring  2  20071214 00:21 
Need help to run stage 1 and stage 2 separately  jasong  GMPECM  9  20071025 22:32 
Stage 1 and stage 2 tests missing  Matthias C. Noc  PrimeNet  5  20040825 15:42 